The determination of hydrogen content in power reactor materials is a component of an overall surveillance program. Unfortunately, techniques that accurately and nondestructively measure hydrogen content at parts-per-million (ppm) levels have not previously been available. One possible hydrogen measuring technique is based upon the “notched neutron spectrum technique” that has been implemented by EG&G Idaho to characterize hydrogen content in reactor materials for the U.S. Navy. Modifications to this technique have already been demonstrated that increase its sensitivity and utility, allowing for a current accuracy of 0.4 micrograms of hydrogen per gram of steel or an equivalent weight of 6 micrograms in a typical steel sample. This paper describes further tests that have increased the dynamic range of these measurements and provided verification of the absolute calibration of the method.